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Sunday, January 20, 2013

Study: Chimpanzees Have A Fairness Doctrine

ATLANTA,
Georgia -- Voters were deluged last election cycle by campaign messages
from both Democrats and Republicans as to what each political party
envisioned was economic fair play while at the same time accusing the
other of having policies that were either an unfair distribution of
wealth or simple selfish greed. As it turns out, chimpanzees also have a
version of the "Fairness Doctrine" when it comes to those same
socioeconomic dilemmas.

Researchers at the Yerkes National Primate Research Center at Emory
University are the first to show chimpanzees possess a sense of
fairness that has previously been attributed as uniquely human. Working
with colleagues from Georgia State University, the researchers played
the "Ultimatum Game" with the chimpanzees to determine how sensitive the
animals are to the reward distribution between two individuals if both
need to agree on the outcome.

In the study, researchers tested six adult chimpanzees (Pan
troglodytes) and 20 human children (ages 2–7 years) on a modified
Ultimatum Game. One individual chose between two differently colored
tokens that, with his or her partner's cooperation, could be exchanged
for rewards (small food rewards for chimpanzees and stickers for
children). One token offered equal rewards to both players, whereas the
other token favored the individual making the choice at the expense of
his or her partner. The chooser then needed to hand the token to the
partner, who needed to exchange it with the experimenter for food. This
way, both individuals needed to be in agreement.

Both the chimpanzees and the children responded like adult humans
typically do. If the partner's cooperation was required, the chimpanzees
and children split the rewards equally. However, with a passive
partner, who had no chance to reject the offer, chimpanzees and children
chose the selfish option.

"We used the Ultimatum Game
because it is the gold standard to determine the human sense of
fairness," said first author Darby Proctor. "In the game, one individual needs to propose a reward division to another individual and then have that individual accept the
proposition before both can obtain the rewards. Humans typically offer
generous portions, such as 50 percent of the reward, to their partners,
and that's exactly what we recorded in our study with chimpanzees."

The researchers say the findings, available in an early online
edition of the Proceedings of the National Academy of Sciences (PNAS)
available this week, suggest a long evolutionary history of the human
aversion to inequity as well as a shared preference for fair outcomes by
the common ancestor of humans and apes.

"Until our study, the behavioral
economics community assumed the Ultimatum Game could not be played with
animals or that animals would choose only the most selfish option while
playing," Co-author Frans de Waal said. "We've concluded that chimpanzees not only get very close to the
human sense of fairness, but the animals may actually have exactly the
same preferences as our own species." For purposes of direct comparison,
the study was also conducted separately with human children.

Researchers say that chimpanzees, who are highly cooperative in the wild, likely need to
be sensitive to reward distributions in order to reap the benefits of
cooperation. Thus, this study opens the door for further explorations
into the mechanisms behind this human-like behavior.